Control system



H. D. JAMES.

CONTROL SYSTEM.

APPLICATION FILED DEC.2, 1918.

1,365,322. Patented Jan. 11, 1921.

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{ MW ATTCiRiW I HENRY 1). JAMES, 0F EDGEVJQQD PARK, PENNSYLVANIA,ASSIGNOR TQ WESTING- H0'USE MECTRIG 6a MANUFACTURING- CQItILANY, AGQYEQPOEATIQN @F EENNSYL- VANIA. CQN'TPRQL SYQaTEIE.

gfig ggg S iccification of Letters Patent. Patented Jam, 111 1921,

application .filed'ficceniber 2;, 1918. Serial No. 284,931.

To all whom it may concern."

Be it known that T, Hnnnr lD. JAMns, a citizen of the United States, anda resident of Edgewood Park, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in ControlSystems, of which the following is a specification.

My invention relates to motoncontrol sys tems, I

The object of my invention is to provide a control system with the aidof which it shall be possible to start a motor, to accelcrate it and tocontrol its speed in accordance with predetermined condit ons.

According to my invention, an acceleratingv resistor is short-circuitedby means contactors of the now well known loch out type having thepeculia property being maintained open cu-rent is above a predeterminedvalue and of closing when the current falls to value. I connect theactuating coils of the contactors between different-potential points'cithe sow ing resistor. As the coils become deenergized when the startingresistor is short-circuited, it is necessary to provide some means formaintaining the resistor 'short-circuited. In one form of my invention,T e est this re sult by energizing; the last contactor to close by theelectrornotive force of the motor. According to another form of nayinvention, the actuating coil of the contactcr, or plurality of thecontactors may, afterclosing, be connected directly across the line.

My invention will be made clear nection with the accompanyir j whichFigures 1, 2 and 3 are representations of different vention.

Referring to Figs. 1 and 2, electric rnotor, having; an armature 1 and eshnnt lield= magnet winding 2, is connected between line conductors 3and l, separated by a line con= tactor 5, which is adapted to he closedhy means of an actuating coil 6, the circuit ct which may be closed by amaster switch 7 An accelerating resistor, portions of which areindicated at 8, 9-and 10, is connected in series with the armature 1 andadapted to be short-circuited by a plurality of contactors 11, 12 and13, having actuating coils 14, 15 and 16.

The contactors 11 and 12 of Fin/ 1 are ot the lookout type; that is,when the current flowing through their actuating coils is above apredetermined value, they will be maintained in the illustrated, openpositions; and whenthe current falls to this value, they will close. Thecontactor 13 of the system of Fig. 2 is, like the contactors 11 and 12,a lookout contactor.-..but the circuit of its coil 16 is connected, inseries with a resistor 17 of high resistance, across the line conductors3 and l.

Tn Fig. 1, the actuating coils I l and 15 of the contactors 11 and 12are connected at 18 19, in parallel, acrossthe accelerating resistor.The contactor 11 of Fig. 2 is connected, 19 and 20, between one end ofthe resistor and the point connecting the no? ticns 8 9.05 the resistor,and the contactor 15 is connected at 18 and 19, across the wholeresistor. The contactor 13 of F is adapted to bridge contact members 21,when occupying open position, for the purpose of then closing a circuitfor its ac tuja'ting coil 16-, which extends from the point 18, throughthe contact members and the coil 16, to the point 19. i

The operation of the system shown in 1 may be described as follows.Assuming that the master switch 7 has been closed to cause theenergization of the coil 6, and thereby to cause the closing of thecontactor 5, current will flow from the line conductor 3, through thearmature 1 and the accelerating resistor 8, 9, 10, and the shunt fieldmagnet winding 2, inparallel, to the point 19 and thence, through theline contactor 5, to the line conductor 4*. A shunt circuit is, at sametime, established for the will serve maintain the contactor 12 openeriod of tune until for predetermined the current again ital s, thistime to the closing value of the contactor12. The closing of thiscontactor results in short-cirtill pin

tactors 11 and 12, since they are controlled by the potential differenceof the points 18 and 19. This has no result upon the operation of themotor, however,because of the contactor 13, which will remain closed solong as the counter-electromotiveforce of the motor is above apredetermined value.

If the motor-be started under a moder ately heavy load, the current willfall so rapidly from a high value to a value below that at which thecontactor 11 is adapted to be closed that this contactor will remainopen. The contactors 12 and 13, however, will close in order, as abovedescribed. Similarly, if the motor be started under a light load, thestarting current may drop from a high value to a valuebelow that at'which the contactor 12 is designed to close with the result that thecontactors '11 and 12 will remain open and the accelerating resistorwill be controlled entirely by the counter-electromotive-force contactor13.

I thus provide a system having the requisite kinds of speed controladapted to the load on the motor.

The operation of the system of Fig. 2 is somewhat different, for thetimeof closing of the contactor 11 is controlled, not merely by well knownadjustments of the contactor itself, but also'by the fact that its coil14 is connected across a portion only of the accelerating resistor. Thecontactor 11 will, accordingly, close, before thecontactor 12, toshort-circuit the resistor portion 10.

Upon the closing of this contactor 11, the coil 15 will be controlled bythe potential difference between the. point 18 and the point 22, whichlatter point separates the resistor portions 9 and 10, the resistorportions having been short-circuited by the of the contactor 11. Thecontactor l2 wil then close at the proper time, in accordance withcurrent conditions. as described in connection with the description ofFig. 1, to short-circuit the resistor ortion 9. The coil 16 will now becontrolled by the difference of potential between the oints 18 and 20and, when the contactor 13 nally closes to short-circuit the resistorportion 8, the circuit of the actuating coil 16 will be broken at thecontact members 21 but the coil will continue to be energized by thecircuit extending from the line conductor 3 through the resistor 17 andthe coil 16, to the point 19 and thence, through the contactor 5,.to theline conductor 4. This circuit, though not sufiiciently energized tocause the actuation of the contactor 13 in the first instance, willmaintain the contactor in closed position.

It will be obvious that the contactors 11, 12 and 13 of the-system ofFig. 2 may be connected in parallel, as isthe case with the contactors11 and 12 of Fig. 1, and that the latter co'ntactors may be connected todifferent intermediate points of the accelerating resistor, as in Fig.2.

It will be obvious, too, that the contactor 13 of Fig. 1 may be replacedby a contactor like that numbered 13 in Fig. 2. The circuit of each ofthe coils 1 1, 15 and 16, in that event, since they will be allconnected in parallel, and including contact members like those numbered21 in Fig. 2, will be closed when the contactor 13 occupies its openposition. This is diagrammatically represented in Fig. 3 in a systememploying but two contactors. Other modifications, too, will occur tothose skilled in the art, and I desire, therefore that the a)- pendedclaims shall be construed broadly except in so far as limitations may beexpressly imposed therein.

I'claim as my invention:

1. The combination with an electric motor and a resistor in circuittherewith, of a plurality of switches for controlling said resistor, oneof said switches havingv lockout characteristics and another of saidswitches being so connected as to close in accordance with the value ofthe current traversing said motor and to be thereafter responsive to thevalue of the counter-electromotive force of said motor.

2. The combination with an electric motor, of means for'controlling thesame comprising a starting resistor, a plurality of electromagneticswitches for controlling the resistor which hold open when theenergizing current is relatively high and close when the currentdecreases to a lower value, and connections whereby the energizingwinding of one switch is connected between points of different potentialof said resistor to cause it to close when the current through theresistor decreases and the winding of another switch is thereuponeffective to control said other switch.

3. The combination with an electric motor, of means for controlling thesame com prising a starting resistor, a plurality of electromagneticswitches for controlling the resistor which hold open when theenergizing current is relatively high and close when the currentdecreases to a lower value, each having an energizing coil adjusted andconnected between points of different potential of said resistor tocause them to successively close as the current through the resistordecreases.

4. Thecombination within electric motor having a resistor associatedtherewith, of a pair of electromagnetic switches for controlling saidresistor which hold open when the energizing current is relatively highand close when the current decreases to a lower value, one of saidswitches having an actuating coil connected between points of differentpotential of said resistor, and the other of said switches having a coilthat is energized to maintain said other'switch closed during the normaloperation of said motor.

5. The combination with an electric motor having a resistor associatedtherewith, and a source of energy for said motor, of an electromagneticswitch for controlling said resistor which holds open when theenergizing current is relatively high and closes when the currentdecreases to a lower value and having an actuating-coil connected'between points of different potential of said resistor, and means forenergizing said coil by energy from said source to maintain said switchclosed llp0n the closing of said switch.' 1

6. The combination with an electric motor having a resistor associatedtherewith, of a plurality of electromagnetic switches for controllingsaid resistor which hold open when the energizing current is relativelyhigh and close when the current decreases to alower value, each havingan actuating coil connected across different portions of said resistor,and connections whereL y, upon the closing of one of said switches, aportion of said resistor, across which the coil of another of saidswitches is connected, 5s short-circuited. 4

7. The combination with an electric motor having a resistor associatedtherewith, of a switch, for controlling said resistor which holds openwhen the energizing current is relatively high and closes when thecurrent decreases to a lower value, and having an actuatlng coilconnected between polnts of different potential of said resistor andanother switch for controlling said resistor having an actuating coilresponsive to the counter-electromotive force of said motor.

In testimony whereof, I have hereunto subscribed my name this 27th dayof Nov.,

HENRY D. JAMES.

